What is the output of the following C program on a 64-bit system? #include #include int main(void) { int *p = malloc(10 * sizeof *p); if (p == NULL) return 1; printf("%zu %zu\n", sizeof p, sizeof *p); free(p); return 0; }

Memory Allocation · Predict the Output · Question 1

sizeof p vs sizeof *p after malloc – output Answer, explanation & discussion

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Question 1 Back to Exercise

What is the output of the following C program on a 64-bit system?

main.c

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int *p = malloc(10 * sizeof *p);
    if (p == NULL)
        return 1;
    printf("%zu %zu\n", sizeof p, sizeof *p);
    free(p);
    return 0;
}

A 8 4 Correct
B 40 4
C 40 40
D 8 40

Correct Answer: Option A

sizeof p is the size of the pointer variable (8 bytes); sizeof *p is one int (4). Nothing in C remembers that the block holds 40 bytes – you must keep the count yourself.

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sizeof p vs sizeof *p after malloc – output Answer, explanation & discussion

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